This proposal will investigate the cytoplasmic determinants (morphogens) in the Ascidian egg that appear to regulate the differentiation of three histospecific enzymes in the embryo: muscle acetylcholinesterase, endodermal alkaline phosphatase, and pigment cell tyrosinase. These histochemically detectable enzymes will be used as markers in experiments to reinvestigate early cytoplasmic changes in the egg which are believed to affect localization and subsequent segregation of morphogens. Other studies are concerned with chemical identification of two of the morphogens, and with establishing some of their functional properties. The proposal seeks to authenticate the following statements. A movement and subsequent localization of morphogens takes place during fertilization. Localization and segregation of maternal mRNA occurs in the egg and embryo. When cytoplasm is caused to mis-segregate at cleavage there is a change in cell lineage determination. Morphogens have pleiotropic effects in tissues, and also determine the amount of enzyme made. The alkaline phosphatase morphogen is a maternal mRNA for the enzyme, and the acetylcholinesterase morphogen is also an RNA. The central aim of this program is to identify regulatory elements in cell differentiation of Ascidian embryos that are probably shared by all animal groups.